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Mark Walton; Neural mechanisms of oculomotor abnormalities in strabismus. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3433.
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Presentation Description :
In infantile strabismus the eyes are misaligned in early postnatal life, a time in which the tuning properties of many neurons are highly sensitive to environmental influences. As a result, many visual cortical neurons that would normally be responsive to both eyes develop strong preferences for a single eye. This means a loss of binocular disparity signals that, in turn, deprives the vergence system of a crucial sensory input. This talk will explore recent evidence that this results in a cascade of abnormalities that affects brainstem neurons involved in smooth pursuit, saccades, and vergence eye movements. For example, ongoing experiments in our laboratory suggest that some near response cells carry contextually inappropriate vergence velocity signals during a saccade task on a tangent screen.We will discuss possible scenarios by which loss of disparity sensitive neurons in cortex and abnormalities of disparity vergence may adversely affect other eye movement systems. For example, these abnormalities may deprive crucial oculomotor regions, such as cerebellum, of the error signals needed to guide the development of normal tuning. In pattern strabismus, the horizontal and vertical misalignments vary with eye position along the orthogonal axis. This talk will discuss the results of recent experiments suggesting that this abnormality may be associated with a general breakdown of directional tuning in brainstem oculomotor areas. For example, horizontal and vertical rectus motoneurons carry monocular signals related to cross-axis smooth pursuit. Similarly, microstimulation of several brainstem areas evokes directionally disconjugate eye movements. Some neurons recorded in these areas show abnormal directional tuning.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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